package win.demonlegion.util;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Arrays;

/**
 * @author https://www.cnblogs.com/nihaorz/p/10690643.html
 * @description Rsa 工具类，公钥私钥生成，加解密
 * @date 2020-05-18
 **/
@Slf4j
public class RsaUtils {
    /**
     * 公钥解密
     *
     * @param publicKeyText 公钥
     * @param text 待解密的信息
     * @return /
     * @throws Exception /
     */
    public static String decryptByPublicKey(String publicKeyText, String text) throws Exception {
        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKeyText));
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, publicKey);
        byte[] result = cipher.doFinal(Base64.decodeBase64(text));
        return new String(result);
    }

    /**
     * 分段加密
     * @param publicKeyText
     * @param text
     * @return
     */
    public static String encrypt(String publicKeyText, String text) throws Exception {
        // 将Base64编码后的公钥转换成PublicKey对象
        byte[] buffer = Base64.decodeBase64(publicKeyText);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        // 加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] inputArray = text.getBytes();
        int inputLength = inputArray.length;
        // 最大加密字节数，超出最大字节数需要分组加密
        int MAX_ENCRYPT_BLOCK = 117;
        // 标识
        int offSet = 0;
        byte[] resultBytes = {};
        byte[] cache = {};
        while (inputLength - offSet > 0) {
            if (inputLength - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(inputArray, offSet, MAX_ENCRYPT_BLOCK);
                offSet += MAX_ENCRYPT_BLOCK;
            } else {
                cache = cipher.doFinal(inputArray, offSet, inputLength - offSet);
                offSet = inputLength;
            }
            resultBytes = Arrays.copyOf(resultBytes, resultBytes.length + cache.length);
            System.arraycopy(cache, 0, resultBytes, resultBytes.length - cache.length, cache.length);
        }
        return Base64.encodeBase64String(resultBytes);
    }

    /**
     * 分段解密
     * @param privateKeyText
     * @param text
     * @return
     */
    public static String decrypt(String privateKeyText, String text) throws Exception {
        try
        {
            // 对私钥解密
            byte[] privateKeyBytes = Base64.decodeBase64(privateKeyText);
            // 获得私钥
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
            // 获得待解密数据
            byte[] data = Base64.decodeBase64(text);
            KeyFactory factory = KeyFactory.getInstance("RSA");
            PrivateKey privateKey = factory.generatePrivate(keySpec);
            // 对数据解密
            Cipher cipher = Cipher.getInstance(factory.getAlgorithm());
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            // 返回UTF-8编码的解密信息
            int inputLen = data.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            // 最大解密字节数，超出最大字节数需要分组解密
            int MAX_DECRYPT_BLOCK = 128;
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 对数据分段解密
            while (inputLen - offSet > 0)
            {
                if (inputLen - offSet > MAX_DECRYPT_BLOCK)
                {
                    cache = cipher.doFinal(data, offSet, MAX_DECRYPT_BLOCK);
                } else
                {
                    cache = cipher.doFinal(data, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_DECRYPT_BLOCK;
            }
            out.close();
            return out.toString("UTF-8");
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
        return null;
    }

    /**
     * 私钥加密
     *
     * @param privateKeyText 私钥
     * @param text 待加密的信息
     * @return /
     * @throws Exception /
     */
    public static String encryptByPrivateKey(String privateKeyText, String text) {
        try {
            PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyText));
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, privateKey);
            byte[] result = cipher.doFinal(text.getBytes());
            return Base64.encodeBase64String(result);
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
        return null;
    }

    /**
     * 私钥解密
     *
     * @param privateKeyText 私钥
     * @param text 待解密的文本
     * @return /
     * @throws Exception /
     */
    public static String decryptByPrivateKey(String privateKeyText, String text) {
        try {
            PKCS8EncodedKeySpec pkcs8EncodedKeySpec5 = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKeyText));
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec5);
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            byte[] result = cipher.doFinal(Base64.decodeBase64(text));
            return new String(result);
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
        return null;
    }

    /**
     * 公钥加密
     *
     * @param publicKeyText 公钥
     * @param text 待加密的文本
     * @return /
     */
    public static String encryptByPublicKey(String publicKeyText, String text) {
        try {
            X509EncodedKeySpec x509EncodedKeySpec2 = new X509EncodedKeySpec(Base64.decodeBase64(publicKeyText));
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec2);
            Cipher cipher = Cipher.getInstance("RSA");
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            byte[] result = cipher.doFinal(text.getBytes());
            return Base64.encodeBase64String(result);
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
        return null;
    }
}
